Photovoltaic solar cells convert light energy into electricity. Because solar cells are nonpolluting and solar energy is abundant, solar cells are an extremely attractive source of electricity. However, before widescale use can be made of solar cells, their cost must be reduced to make them economically competitive with conventional sources of electricity.
Solar cells are typically made from solid wafers of solar cell material like silicon. Because silicon and other solar cell materials are expensive, one method of reducing the cost of solar cells is to use less solar cell material by applying a thin film of the material on a substrate. Present methods for applying a thin film of solar cell material on a substrate, like chemical vapor deposition, are typically high temperature processes. For example, chemical vapor deposition is usually performed at temperatures above 1,000.degree. C. When using such a process, the temperature of the substrate is raised to the deposition temperature. Consequently, these processes limit the types of substrate materials that can be used for making solar cells. For instance, while quartz and glass, which can withstand high temperatures, may be suitable as substrate material, other less expensive materials like plastics may be unsuitable.
An additional problem with present methods of making thin film solar cells is that they do not provide effective means for selective deposition of solar cell and electrical contact material. As solar cells can be designed to be intricately connected with other solar cells, a method of selectively coating the substrate should be provided to facilitate the connections.
Thus, a need has arisen for a method of applying solar cell and electrical contact material on substrates that does not substantially raise the temperature of the substrates, thereby allowing use of a wide range of substrate materials, including inexpensive plastics. Further, there is a need for an effective method for selectively depositing solar cell and electrical contact material on substrates to allow intricate connections between solar cells.